A Diffusion Cell Method for Studying Heterogeneous Kinetics in the Chemical Reaction/Diffusion Controlled Region. Kinetics of C + CO2→ 2CO at 1200-1600° C

A new rigid tricyanate ester consisting of seven conjugated aromatic units is synthesized, and its structure is confirmed by X-ray analysis. This ester undergoes thermally stimulated polymerization in a liquid state. Conventional and temperature-modulated differential scanning calorimetry techniques are employed to study the polymerization kinetics. A transition of polymerization from a kinetic- to a diffusion-controlled regime is detected. Kinetic analysis is performed by combining isoconversional and model-based computations. It demonstrates that polymerization in the kinetically controlled regime of the present monomer can be described as a quasi-single-step, auto-catalytic, process. The diffusion contribution is parameterized by the Fournier model. Kinetic analysis is complemented by characterization of thermal properties of the corresponding polymerization product by means of thermogravimetric and thermomechanical analyses. Overall, the obtained experimental results are consistent with our hypothesis about the relation between the rigidity and functionality of the cyanate ester monomer, on the one hand, and its reactivity and glass transition temperature of the corresponding polymer, on the other hand.

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On the Role of Diffusion in the Oxidation of Fe, Ni, Co and the Fe-Sn Alloy by Calcium and Sodium Sulfates

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.258-260.63 ◽

2006 ◽

Vol 258-260 ◽

pp. 63-67

Author(s):

V.M. Chumarev ◽

V.P. Maryevich ◽

V.A. Shashmurin

Keyword(s):

Co Oxidation ◽

Chemical Reaction ◽

Diffusion Processes ◽

Transport Processes ◽

Diffusion Transport ◽

Sodium Sulfates ◽

Product Forms ◽

Kinetics Of ◽

Dominant Part

Diffusion processes play a dominant part in the macro kinetics of Fe, Ni and Co oxidation by calcium and sodium sulfates. Here, the reaction product forms a compact covering which spatially divides the reagents on the surface in the same way as in the oxidation and sulfidization of metals by oxygen and sulfur. Therefore, it is possible to assume in advance that interaction of metals with calcium and sodium sulfates will be determined not by the actual chemical reaction properly but by the diffusion transport processes.

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Measurement of the Effective Diffusivity in Porous Media by the Diffusion Cell Method

Catalysis Reviews ◽

10.1080/01614949608006458 ◽

1996 ◽

Vol 38 (2) ◽

pp. 189-247 ◽

Cited By ~ 30

Author(s):

IN-SOO PARK∗ ◽

DUONG D. DO ◽

ALIRIO E. RODRIGUES

Keyword(s):

Porous Media ◽

Effective Diffusivity ◽

Diffusion Cell ◽

Cell Method

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Primary products and processes in the γ-radiolysis of 2-methyltetrahydrofuran

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1965.0107 ◽

1965 ◽

Vol 285 (1402) ◽

pp. 319-338 ◽

Cited By ~ 32

Keyword(s):

Glassy Phase ◽

Kcal Mole ◽

Radical Species ◽

Molecule Reaction ◽

Positive Ions ◽

Primary Products ◽

Diffusion Controlled ◽

Thermal Bleaching ◽

The Matrix ◽

Kinetics Of

From a study of the u. v., visible, near i. r. and e. s. r. spectra induced by γ -irradiation at 77°K in glassy MTHF and in glassy MTHF containing various additives and from a study of controlled temperature increases on these spectra, the following conclusions are drawn. (1) The primary products of the radiolysis are electrons ( e - ) and positive ions ( MTHF + ) which undergo a rapid ion-molecule reaction to give O CH 3 radicals ( R ⋅). (2) e - can either be trapped in the glassy MTHF matrix or can be captured by either napththalene, ferric chloride, carbon tetrachloride, nitrous oxide or trans -stilbene if these substances are present. (3) The e - T are bleachable by light or heat and disappear independently of the radicals R⋅ without either augmentation of R⋅ or the production of any new radical species. (4) e - T and R⋅ disappear thermally and independently by second-order reactions, the rate constants being K e - + e - (M -1 S -1 ) = 10 12⋅4±1⋅1 exp ─ [0⋅85 ± 0⋅10 kcal/mole/ R ( T ─ 75)] and K R˙ + R˙ (M -1 S -1 ) = 10 13⋅3±1⋅4 exp ─ [1⋅20 ± 0⋅15 kcal/mole/ R ( T ─ 75)]. These rate expressions suggest that both reactions are diffusion controlled at low temperatures in the glassy phase. (5) The kinetics of the thermal bleaching of e - T indicate that the electrons migrate distances of about 150 Å from their parent positive ions before being trapped in the matrix. (6) The effect of FeCl 3 in reducing the formation of e - T at 77°K and its lack of effect on the thermal bleaching of e - T suggests that the reaction e - + FeCl 3 → FeCl 2 + Cl - only occurs before the electron is thermalized.

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Study of kinetics of reaction of lignin model compounds with propylene oxide

Holzforschung ◽

10.1515/hf.2008.025 ◽

2008 ◽

Vol 62 (2) ◽

pp. 169-175 ◽

Cited By ~ 3

Author(s):

Krishna K. Pandey ◽

Tapani Vuorinen

Keyword(s):

Chemical Reaction ◽

Propylene Oxide ◽

Aqueous Media ◽

Reaction Products ◽

Model Compounds ◽

Rapid Reduction ◽

Visible Absorption ◽

Lignin Model Compounds ◽

Lignin Model ◽

Kinetics Of

Abstract The etherification of phenolic groups has been found to inhibit photodegradation in wood and lignin rich pulps. The precise understanding of kinetics of chemical reaction between lignins or their model compounds and the etherifying agent is the first step for developing a viable modification procedure. In this study, we have investigated the reaction of lignin model compounds (namely, phenol and guaiacol) with propylene oxide in aqueous media. The kinetics of etherification reaction was studied under varying pH conditions in the temperature range 30–60°C. The etherified reaction products were characterized by gas chromatogram-mass spectrum (GC-MS). The extent of etherification of phenols and the rate of chemical reaction was followed by UV-Visible absorption spectroscopy. The reaction between lignin model compounds and propylene oxide was indicated by a rapid reduction in the absorbance accompanied by the development of a new band corresponding to etherified products. The reaction kinetics was investigated at pH ∼12 under the condition of excess concentration of propylene oxide. The reaction followed first order kinetics and rate constants increased linearly with an increase in the temperature and concentration of propylene oxide. The MS fragment data of reaction product support the proposed reaction scheme. The activation energy of the reaction of propylene oxide with phenol and guaiacol, calculated with the Arrhenius equation, was 56.2 kJ mol-1 and 45.4 kJ mol-1, respectively.

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Investigation of the Kinetics of Sulfite Oxidation on by-Production Recovery Process in WFGD

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.610-613.1980 ◽

2012 ◽

Vol 610-613 ◽

pp. 1980-1985 ◽

Cited By ~ 3

Author(s):

Hong Jian Xu ◽

Shu Fang Wang ◽

Wei Guo Pan ◽

Rui Tang Guo

Keyword(s):

Chemical Reaction ◽

Oxidation Kinetics ◽

Reaction Rate ◽

Recovery Process ◽

Orthogonal Test ◽

Sulfite Oxidation ◽

Air Ventilation ◽

Kinetics Of

The limestone-lime washing technology is the most widely used WFGD process, which normally we adopt to control the discharge of SO2 caused by coal’s combustion. Through the research on the oxidation kinetics of sulfite in this paper, it is indicated that macroscopic chemical reaction which responses to rate of sulfite is 1/2. And the results of orthogonal test can be concluded that: to the extent influence of oxidization reaction rate, the influences of temperature is the most significant, and influences of stirred speed is nearly negligible. The optimized operation factors may be shown as that temperature is controlled at 40°C, air ventilation is at 88ml/min,pH is 4.5 and stir speed is 500 r/min.

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